Conclave 2026

Guy Borenstein, FGA EGG, is Stuller's Director of Gemological Research and Lab Services, leading the company's comprehensive diamond screening and gemological testing operations across its global facilities.
In addition to directing fully equipped, high-volume gemological laboratory operations, Borenstein's other responsibilities include heading the company's diamond screening array, testing more than 5 million units a year; developing new testing techniques and protocols for diamonds and gemstones; and training associates at all company facilities involved in the processes. He continually researches emerging technology-based screening and identification solutions and implements the best practices into the company's internal workflows.

Before joining Stuller, Borenstein served for 15 years in various gemological capacities, including Chief Gemologist in two gemological laboratories, VP of Gemological Services in the gem color analysis startup Gemewizard, FGA Gemmology Diploma tutor at Gem-A (Gemmological Association of Great Britain), and consultant to numerous institutes and companies worldwide.

Borenstein also published numerous scientific articles in leading journals, including GIA's Gems and Gemology and Gem-A's Journal of Gemmology, covering new discoveries in the field of gemology.